Power management in wireless tracking device operating with restricted power source

ABSTRACT

A wireless tracking device operating in at least two modes to reduce power consumption and extend the operable period of the wireless tracking device. In an active mode, the wireless tracking device samples sensor signals at a higher resolution and may also actively communicate with a remote device via wireless connection. In a hibernation mode, most of the components or modules in the wireless tracking device are shut down to reduce power consumption. The wireless tracking device may switch to the active mode when a predetermine event is detected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/610,791, filed Jun. 1, 2017, which is a continuation of U.S.application Ser. No. 12/980,171, filed Dec. 28, 2010, now U.S. Pat. No.9,696,429, issued Jul. 4, 2017, each of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to managing operations of a wireless trackingdevice with a restricted power source, more specifically to operatingthe wireless tracking device in more than one mode of operation toreduce power consumption and prolong its operational time.

2. Background of the Invention

Wireless tracking devices are employed to track locations and conditionsof various assets. Such wireless tracking devices are often mounted onthe assets or placed in the vicinity of the assets. As the assets aretransported or are exposed to changing environment, the wirelesstracking devices detect the location and/or sense changing conditions ofthe assets. Then, the wireless tracking devices send wireless messagesindicating the locations and/or other environment parameters of theassets to a remote monitoring station. Based on the collectedinformation, the remote monitoring station may prompt actions such assending reports to customers, taking remedial actions to preventdeterioration of the assets, and initiating retrieval of stolen assets.

Generally, a wireless tracking device includes various components andsensors enclosed in a casing. The casing provides robust protectionagainst dirt or other contaminants as well as external forces. Thewireless tracking device may include various components such astemperature sensors, humidity sensors, light sensors, accelerometers,gyroscopes, magnetometers, controllers, GPS modules and wirelesscommunication modules. These components or modules may consume powerduring their operations. Some wireless tracking devices include sensorsto accommodate diverse applications whereas other wireless trackingdevices are equipped with fewer types of sensors selected for specificapplications.

To provide power to these components and modules, a wireless trackingdevice includes a restricted power source such as batteries or solarcells. In many cases, the wireless tracking devices operate inenvironments where access to other power sources is unavailable. Thewireless tracking devices often rely on the restricted power source fortheir operations. Hence, to increase the operable time of a wirelesstracking device, it is necessary to reduce the power consumption of itscomponents.

SUMMARY OF THE INVENTION

Embodiments relate to a wireless tracking device that operates in atleast two modes of operation to reduce power consumption. In ahibernation mode, the wireless tracking device turns off the componentsconsuming a large amount of power to preserve power. The wirelesstracking device is intermittently placed in an active mode wherecomponents consuming a large amount of power are turned on. When anevent is detected, the wireless tracking device switches from thehibernation mode to the active mode to track locations or detect changesin its environment. The wireless tracking device may revert back to thehibernation mode if no further events are detected or a preset time iselapsed.

In one embodiment, the components turned off in the hibernation modeinclude a locating device for determining the location of the wirelesstracking device and a communication module for sending the message overa wireless network. The locating device and the communication moduleconsume a large amount of power, and hence, these components areintermittently operated in the active anode to preserve power.

In one embodiment, the wireless tracking device includes twocontrollers. One controller consumes less power than the othercontroller. The controller consuming less power remains turned on inboth the active mode and the hibernation mode. In contrast, thecontroller consuming more power is turned on selectively during theactive mode to control components that consume a large amount of power.

In one embodiment, a geofence is established for an area having poorconnectivity to the wireless network. The wireless tracking moduledetermines proximity to the geofence, and switches to the active mode ata higher frequency to detect whether the wireless tracking module hasentered the geofence and to send updated messages before the wirelesstracking device enters the geofence.

The features and advantages described in the specification are not allinclusive and, in particular, many additional features and advantageswill be apparent to one of ordinary skill in the art in view of thedrawings, specification, and claims. Moreover, it should be noted thatthe language used in the specification has been principally selected forreadability and instructional purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram illustrating a wireless tracking devicein a vehicle, according to one embodiment.

FIG. 2 is a block diagram illustrating a wireless tracking device,according to one embodiment.

FIG. 3 is a diagram illustrating a method of operating the wirelesstracking device in more than one mode, according to one embodiment.

FIG. 4 is a diagram illustrating a geofence associated with differentmodes of operation, according to one embodiment.

FIG. 5 is a flowchart illustrating the process of switching between theactive mode and the hibernation mode when the geofence is implemented.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments described herein provide a wireless tracking deviceoperating in at least two modes to reduce power consumption and extendthe operable time of the wireless tracking device. In an active mode,the wireless tracking device activates a communication module forcommunicating with a remote device via wireless connection or othercomponents that consume a large amount of power. In a hibernation mode,the components or modules in the wireless tracking device are shut downto reduce power consumption. The wireless tracking device may switchfrom the hibernation mode to the active mode selectively when apredetermine event is detected.

Example Use of Wireless Tracking Device

FIG. 1 is a diagram illustrating a wireless tracking device 122 in amoving vehicle 120. The wireless tracking device 122 may be located in acargo 126 being transported by the vehicle 120. In this example, thewireless tracking device 122 tracks its location using a GlobalPositioning System (GPS) module that detects signals from satellites110. The wireless tracking device 122 inside cargoes 126 alsocommunicates with a remote monitoring station 128 over a wirelesscommunication channel 130.

The vehicle 120 may carry multiple units of cargoes 126 where each unitis equipped with a wireless tracking device 122. Each cargo 126 may bedestined to a different target location. As a cargo 126 is transported,a wireless tracking device 122 attached to the cargo 126 tracks thelocation of the cargo 126 and environmental conditions surrounding thecargo 126. Then, the location and other environment information aretransmitted to a remote monitoring station 128 in a wireless message.

The environment conditions detected by the wireless tracking device 122may include, but are not limited to, temperature, humidity, light,sound, vibration, tilt, shock, certain types of chemical compounds,pressure, magnetic field, smoke, and movements. The wireless trackingdevice 122 may be configured to detect some or all of these environmentconditions.

The use of wireless tracking device 122 is not limited to moving cargoes126. The wireless tracking device 122 may be used for an object thatremains stationary. In such case, the wireless tracking device 122 isused primarily for detecting environmental conditions surrounding thewireless tracking device 122. Further, the vehicle 120 is merely anexample of a mode of transport. The wireless tracking device 122 and thecargo 126 may be transported using other modes of transport such asvessels, trains or airplanes. Cargo 126 may be any asset transported incommerce, including among other things, envelopes, parcels, expresspackages, boxes, palettes, containers, crates, and specialty goods andmaterials.

Example Structure of Wireless Tracking Device

The wireless tracking device 122 operates in two distinct modes: anactive mode and a hibernation mode. In the active mode, most or all ofthe components in the wireless tracking device 122 are activated. Theactivated components include high power consumption components such as awireless communication module. In the hibernation mode, a fewer numberof components or modules in the wireless tracking device 122 areactivated. Other components or modules are turned off to preserve power.The wireless tracking device 122 switches between the active mode andthe hibernation mode in response to detecting or in anticipation of anevent.

FIG. 2 is a block diagram illustrating the wireless tracking device 122,according to one embodiment. The wireless tracking device 122 mayinclude, among other components, a high power system controller 210, alow power system controller 214, a Global Positioning System (GPS)module 222, a wireless communication module 226, a power manager 230, arestricted power source 234, and various sensors 250 through 262. Thewireless tracking device 122 may include other components notillustrated in FIG. 2 such as an input module or speakers.

The wireless tracking device 122 of FIG. 2 has a dual processorstructure including two controllers: the high power system controller210 and the low power system controller 214. By using the twocontrollers, the power consumption may be reduced in the hibernationmode while obtaining high computing capacity during the active mode.When the wireless tracking device 122 is placed in the active mode, thehigh power system controller 210 becomes active and performs powerintensive operations. Such power intensive operations include, forexample, determining the location of the wireless tracking device 122using the GPS module 222 and communicating wirelessly with the remotemonitoring station 128 via the wireless communication module 226. Duringthe hibernation mode, the wireless tracking device 122, the GPS module222 and the wireless communication module 226 may be disabled to reducepower consumption.

In one embodiment, the low power system controller 214 is embodied asATMEGA 8-bit microcontroller (available from Atmel Corporation of SanJose, Calif.), Energy Micro Gecko micro controller (available fromEnergy Micro AS of Oslo, Norway) or SAM3 (available from AtmelCorporation of San Jose, Cali.). Examples of the high power systemcontrollers 210 include the Marvell PXA series, ARM11, Cortex-A series,or TI DSPs.

In one embodiment, the high power system controller 210 controls theoperation of the GPS module 222 and the wireless communication module226. When the high power system controller 210 is turned off, the GPSmodule 222 and the wireless communication module 226 are alsodeactivated to reduce power consumption.

The low power system controller 214 remains active in both the activemode and the hibernation mode. The low power system controller 214determines whether to place the wireless tracking device 122 in theactive mode or the hibernation mode, as described below in detail withreference to FIG. 3. In one embodiment, the low power system controller214 is connected to low-power consumption components such as sensors 250through 262. The low power system controller 214 continues to receivesensor signals 282 through 294 even in the hibernation mode to avoidlosing meaningful sensor data. However, the sampling rate and thesensitivity of the sensor signals 282 through 294 may be reduced in thehibernation mode to reduce power consumption.

The low power system controller 214 sends commands to the power manager230 to turn on or off power provided to the high power system controller210. When the low power system controller 214 issues a commandindicating that the wireless tracking device 122 should be placed in thehibernation mode, the power manager 230 turns off power to the highpower system controller 210.

The power manager 230 is connected to the power source 234. The powersource 234 may be a restricted power source such as a battery or solarcells. In one embodiment, the power source 234 includes a chargecircuit. The charger circuit receives charging electric current via port238 to charge the battery.

The GPS module 222 may include an antenna and a signal processing unitfor receiving GPS signals. The GPS module 222 operates under the commandof the high power system controller 210 to identify the current locationof the wireless tracking device 122. In one embodiment, the GPS module222 embodies A-GPS (Assisted GPS) which improves the startup performanceor TTFF (Time To First Fix) by utilizing data received via the wirelesscommunication module 226. For this purpose, the GPS module 222 receivesephemeris data from a remote server via the wireless communicationmodule 226.

The wireless communication module 226 includes a transceiver for sendingor receiving data to or from the remote monitoring station 128. Thewireless communication module 226 may establish communicating usingvarious communication protocols such as GSM, WiFi, Bluetooth, Zigbee,UMTS/HSxPA, 3GPP Long Term Evolution (LTE) and WiMAX.

The sensors 250 through 262 detect various physical properties orconditions and send the sensor signals 282 through 294 to the low powersystem controller 214. The sensors in the wireless tracking device 122include, for example, an accelerometer 250, a light sensor 254, atemperature sensor 258 and a humidity sensor 262. The wireless trackingdevice 122 may include other types of sensors to detect differentphysical properties or conditions.

The high power system controller 210 and the low power system controller214 communicate over a data bridge 212. The high power system controller210 may receive the sensor data from the low power system controller214, compiles the sensor data into a message, and sends the message tothe remote monitoring station 128 via the wireless communication module226. On the other hand, the low power system controller 214 receiveslocation information (based on the GPS module 222) from the high powersystem controller 210 or any data (e.g., control commands) received fromthe remote monitoring station 128 via the data bridge 212.

The high power system controller 210 and the low power system controller214 include computer readable storage medium 270 and computer readablestorage medium 272, respectively. The computer readable storage medium270 stores instructions for execution by the high power systemcontroller 210. The computer readable storage medium 272 storesinstructions for execution by the low power system controller 214. Inone embodiment, the computer readable storage media 270, 272 areembodied as a non-volatile memory device (e.g., EEPROM (ElectricallyErasable Programmable Read-Only Memory) or a flash memory), a volatilememory device (e.g., Random Access Memory (RAM)) or a combination ofboth.

The embodiment of FIG. 2 is merely illustrative. Wireless trackingdevices of different configuration may also be used. For example, asingle processor architecture including only a single controller may beused. In the single processor architecture, all the components andsensors are connected and controlled by the single controller. In oneembodiment, the single controller may operate in two modes: an activemode with a higher processing capacity, and a hibernation mode withreduced power consumption. In yet another embodiment, the high powersystem controller 210 and the low power system controller 214 could alsobe implemented in a multi core configuration or via virtualization witha single core.

Power Mode Switching Scheme

FIG. 3 is a diagram illustrating a method of placing the wirelesstracking device 122 in the active mode or the hibernation mode,according to one embodiment. The low power system controller 214receives 310 the sensor signals 282 through 294 from the sensors 250through 262 or the location of the wireless tracking device 122 from theGPS module 222. For this purpose, the low power system controller 214stores instructions for switching power modes in the computer readablestorage medium 272.

Then, the low power system controller 214 determines 312 if one or moreof predetermined events are detected to place the wireless trackingdevice 122 in the active mode. Various types of events may be used forswitching the modes. The wireless tracking device 122 is placed in theactive mode when events of interest to a user are likely to occur orcontinue whereas the wireless tracking device 122 is placed in thehibernation mode when the events of interest are unlikely to occur orcontinue.

If one or more of predetermined events are detected, the low powersystem controller 214 places or maintains 314 the wireless trackingdevice 122 in the active mode. In one embodiment, the predeterminedevents include detection of movement of the wireless tracking device 122by the accelerometer sensor or the speed of the wireless tracking device122 above a threshold. While the wireless tracking device 122 is in theactive mode, the low power system controller 214 may monitor changes inthe location based on GPS signals from the current active mode sessionto determine the speed of the wireless tracking device 122.Alternatively, the low power system controller 214 may compare thelocation of the wireless tracking device 122 with the location of thewireless tracking device 122 in the previous active mode session todetermine the speed of the wireless tracking device 122.

In one embodiment, the wireless tracking device 122 is placed ormaintained 314 in the active mode when external events are detected viathe sensors 250 through 262. The external events refer to eventsoccurring outside the wireless tracking device 122 and may include, forexample, (i) a motion of the wireless tracking device 122 (as detectedby the accelerometer 250), (ii) changes from indoor to outdoor or viceversa (as detected by the light sensor 254), (iii) changes intemperature (as detected by the temperature sensor 258), (iv) changes inthe humidity (as detected by the humidity sensor 262), and (v) detectionof certain chemical compounds or smoke. If such external events aredetected, events of interest are likely to ensue or continue. Hence, thewireless tracking device 122 is maintained in the active mode to capturedata associated with the external events.

In one embodiment, the event may be passing of tune or a signal from atimer indicating a predetermined time. The low power system controller214 may periodically switch the wireless tracking device 122 to theactive mode. The low power system controller 214 switches to the activemode more often or stays in the active mode for a longer time when theaccelerometer 250 sends a signal 282 indicating the movement of thewireless tracking device 122. The wireless tracking device 122 is morelikely to experience significant changes in the environment when thewireless tracking device 122 is being transported. Hence, the wirelesstracking device 122 is placed in the active mode to send more frequentupdates to the remote monitoring station 128. The low power systemcontroller 214 may switch back to the hibernation mode if a certainamount of time is elapsed.

If no significant events are detected for a predetermined amount oftime, the low power system controller 214 places or maintains 318 thewireless tracking device 122 in the hibernation mode. The wirelesstracking device 122 is unlikely to encounter significant changes whenpredetermined events are not detected. Hence, the low power systemcontroller 214 places the wireless tracking device 122 in thehibernation mode to preserve power.

After placing or maintaining 314, 318 the wireless tracking device 122in the active mode or the hibernation mode, the process returns toreceiving 310 the sensor signals or locations.

In one embodiment, more significant events in the sensor signals or moredrastic changes in locations are needed to switch the wireless trackingdevice 122 from the hibernation mode to the active mode compared to theevents for maintaining the wireless tracking device 122 in the activemode. The sensitivity of sensors (e.g., the accelerometer 250) islowered in the hibernation mode to avoid the wireless tracking device122 from waking up to the active mode due to minor variances in thesensor signals.

In contrast, if the wireless tracking device 122 is currently in theactive mode, the sensitivity of the sensors is increased. The fact thatthe wireless tracking device 122 is currently in the active modeindicates that the wireless tracking device 122 is likely to experienceother significant events. By adjusting the sensitivity to sensor signalsand location changes based on the mode of the wireless tracking device122, the wireless tracking device 122 may be prevented from waking updue to insignificant events while retaining the chance of detectingsignificant events.

Geofencing of Wireless Tracking Device

The wireless tracking device 122 may move through a geographic regionwhere wireless communication is not available or where reception of thewireless communication is poor. In one embodiment, such geographicregion may be established as a goefence in which the wireless trackingdevice 122 does not attempt to communicate with the remote monitoringstation 128. A geofence herein refers to a geographical areaartificially defined for one purpose or the other. By avoidingcommunication in the geofenced area, power consumption associated withattempting to communicate with the remote monitoring station 128 in apoor reception area can be avoided. In addition, this feature be used tosatisfy certain regulatory requirements about RF transmissions inparticular areas.

FIG. 4 is a diagram illustrating a geofence 410 associated with wirelesscommunication of the wireless tracking device 122 where wirelesscommunication is unavailable or the signal reception is poor. Within thegeofence 410, the wireless tracking device 122 does not attempt tocommunicate with the remote monitoring station 128. Data collected forevents while the wireless tracking device 122 remains in the geofence410 are stored and then transmitted to the remote monitoring station 128when the wireless tracking device 122 leaves the geofence 410. In FIG.4, region 420 represents an area where the wireless communication of thewireless tracking device 122 is available with good reception.

In the example of FIG. 4, the wireless tracking device moves from pointX to point Z. While the wireless tracking device 122 is in the region420 and distanced away from the geofence 410 (represented by line X-Y),the wireless tracking device 122 switches to the active mode at a firstfrequency (i.e. sampling interval). As the wireless tracking device 122approaches the geofence 410 (represented by line Y-Z), the wirelesstracking device 122 switches to the active mode at a second frequencyhigher than the first frequency (i.e., the wireless tracking device 122is placed in the active mode more often). For example, the wirelesstracking device 122 may switch from the hibernation mode to the activemode every 10 minutes when the wireless tracking device 122 is travelingfrom point X to point Y. The same wireless tracking device 122 mayswitch from the hibernation mode to the active mode every 5 minutes whenthe wireless tracking device 122 is traveling from point Y to point Z.

In one embodiment, the wireless tracking device 122 gradually switchesto active mode with increasing frequency or stays in the active mode fora longer time as the wireless tracking device 122 approaches thegeofence 410.

FIG. 5 is a flowchart illustrating the process of switching between theactive mode and the hibernation mode when the geofence 410 isimplemented. First, the wireless tracking device 122 switches 508 to theactive mode. In the active mode, the low power system controller 214determines 510 the location, the moving direction and the speed of thewireless tracking device 122. Based on the location, the movingdirection and the speed of the wireless tracking device 122, thewireless tracking device 122 computes 514 the estimated time that thewireless tracking device 122 will arrive at the region of the geofence410.

Based on the estimated time of arrival at the region of the geofence410, the interval for switching to the active mode is determined 518.After any process in the current active mode is finished or preset timefor staying in the active mode is elapsed, the wireless tracking device122 switches 522 to the hibernation mode.

Then the wireless tracking device 122 determines 526 whether it is timeto switch to the active mode based on the computed interval. If it istime to switch to the active mode, the process proceeds to switch 508the wireless tracking device 122 to the active mode and repeats thesubsequent steps. If it is not yet time to switch to the active mode,the wireless tracking device 122 remains 522 in the hibernation mode.

By adjusting the interval for placing the wireless tracking device 122in the hibernation mode based on the estimated time of arrival at a poorwireless signal reception area, the wireless tracking device 122 cancontinue to update the remote monitoring station with wireless messageswithout using excessive amount of power.

What is claimed is:
 1. A wireless tracking device, comprising: alocating device configured to determine a location of the wirelesstracking device; at least one controller coupled to the locating device,the at least one controller configured to: determine a first estimateddistance to a location of a geofence; compute, based on the determinedfirst distance, a first estimated time of arrival to the location of thegeofence; determine, based on the first estimated time of arrival, afirst interval for switching the wireless tracking device between afirst mode and a second mode; determine a second estimated distance tothe location of the geofence; compute, based on the determined seconddistance, a second estimated time of arrival to the location of thegeofence; determine, based on the second estimated time of arrival, asecond interval for switching the wireless tracking device between thefirst mode and the second mode; determine an estimated period of timethe wireless tracking device will be within the geofence; and inresponse to determining that the second estimated time of arrival haselapsed, maintain the wireless tracking device in the first mode for theestimated period of time; wherein the second mode consumes more powerthan the first mode.
 2. The wireless tracking device of claim 1, furthercomprising a communication module operable in the second mode but notthe first mode and configured to send a message indicating the locationof the wireless tracking device via a wireless network.
 3. The wirelesstracking device of claim 2, wherein the at least one controllercomprises a first controller and a second controller consuming morepower than the first controller during operation.
 4. The wirelesstracking device of claim 3, wherein the second controller is configuredto operate the locating device and the communication module.
 5. Thewireless tracking device of claim 4, wherein the first controller isconfigured to turn off the second controller and the locating device,and the communication module in the first mode.
 6. The wireless trackingdevice of claim 2, further comprising a restricted power source forproviding power to the locating device, the at least one controller, andthe communication module.
 7. The wireless tracking device of claim 2,wherein the locating device receives ephemeris data from a remote servervia the communication module.
 8. The wireless tracking device of claim1, wherein the locating device comprises a Global Positioning System(GPS) module.
 9. The wireless tracking device of claim 1, wherein the atleast one controller is configured receive a signal from a timerindicating that the first estimated time of arrival has elapsed.
 10. Thewireless tracking device of claim 1, wherein the at least one controlleris configured receive a signal from a timer indicating that the secondestimated time of arrival has elapsed.
 11. The wireless tracking deviceof claim 1, wherein maintaining the wireless tracking device in thefirst mode for the estimated period of time is based on a size of thegeofence.
 12. The wireless tracking device of claim 1, whereinmaintaining the wireless tracking device in the first mode for theestimated period of time is based on an expected signal reception withinthe geofence.
 13. The wireless tracking device of claim 1, furthercomprising a sensor configured to generate a signal representing acondition or a property associated with the wireless tracking device.14. The wireless tracking device of claim 13, wherein the sensorcomprises an accelerometer.
 15. A method of operating a wirelesstracking device, comprising: determining a first estimated distance to alocation of a geofence; computing, based on the determined firstdistance, a first estimated time of arrival to the location;determining, based on the first estimated time of arrival, a firstinterval for switching the wireless tracking device between a first modeand a second mode; determining a second estimated distance to thelocation; computing, based on the determined second distance, a secondestimated time of arrival to the location; determining, based on thesecond estimated time of arrival, a second interval for switching thewireless tracking device between the first mode and the second mode;determining an estimated period of time the wireless tracking devicewill be within the geofence; and in response to determining that thesecond estimated time of arrival has elapsed, maintaining the wirelesstracking device in the first mode for the estimated period of time;wherein the second mode consumes more power than the first mode.
 16. Themethod of claim 15, further comprising at least one controllerconfigured receive a signal from a timer indicating that the secondestimated time of arrival has elapsed.
 17. The method of claim 15,maintaining the wireless tracking device in the first mode for theestimated period of time is based on a size of the geofence.
 18. Themethod of claim 15, wherein maintaining the wireless tracking device inthe first mode for the estimated period of time is based on an expectedsignal reception within the geofence.
 19. A non-transitorycomputer-readable storage medium structured to store instructionsexecutable by a processor in a wireless tracking device, theinstructions, when executed cause the processor to: determine a firstestimated distance to a location of a geofence; compute, based on thedetermined first distance, a first estimated time of arrival to thelocation; determine, based on the first estimated time of arrival, afirst interval for switching the wireless tracking device between afirst mode and a second mode; determine a second estimated distance tothe location; compute, based on the determined second distance, a secondestimated time of arrival to the location; determine, based on thesecond estimated time of arrival, a second interval for switching thewireless tracking device between the first mode and the second mode;determine an estimated period of time the wireless tracking device willbe within the geofence; and in response to determining that the secondestimated time of arrival has elapsed, maintain the wireless trackingdevice in the first mode for the estimated period of time; wherein thesecond mode consumes more power than the first mode.
 20. Thenon-transitory computer-readable storage medium of claim 19, whereinmaintaining the wireless tracking device in the first mode for theestimated period of time is based on a size of the geofence.